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Sound Waves – How They Can Hurt You & How to Protect Yourself

Back in 2007, in response to a U.S. military project, Danley Sound Labs created the Matterhorn, a subwoofer speaker bigger than a pickup truck. At its mouth, the Matterhorn prototype generated 160 decibels, powerful enough to destroy the human ear instantly. Three football fields away, the speaker projected 105 decibels, equivalent to running a lawn mower next to your ear. When the Matterhorn was first demonstrated, officials would not allow Danley to turn the speaker up very far for fear of structurally damaging the surrounding building.

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[column size=”1/2″ class=”right”]Fortunately, commercial versions of the Matterhorn are scaled down to safer levels. But there’s a lesson in this story: Sound is a physical force that must be respected and handled responsibly.
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[/columns]The Science of Sound

Sound is the energy produced when things vibrate, forcing a surrounding medium (such as air) to vibrate as well. The vibrating medium travels in cycles, first compressing as the vibrating object moves outward, and then expanding to fill the space left by the object as it retreats inward.

When diagrammed mathematically, these cycles take the shape of a whip, forming a sine wave with crests and troughs. Points on the X axis midway between each crest and trough, known as nodes, represent where the medium hosting the wave would normally be if the vibration were not disturbing it. The vertical distance between a node and a crest or trough is known as the amplitude and represents degree of disturbance. The horizontal distance between one crest or trough and another is called the wavelength. The number of crests or troughs that pass a given point per second is the frequency. Frequency is calculated by dividing the velocity of the wave by its wavelength and is measured in hertz. The power carried by a sound wave per unit area is called its intensity. Intensity is measured in decibels.

When these waves are perceived by the human ear, the loudness of a sound depends largely on its amplitude. The pitch of a sound depends on its frequency. The quality of a sound depends on how harmonic the synchronization is between the phases of the primary wave produced by the vibrating object and secondary waves produced by different parts of the vibrating object, known as overtones. A piano sounds different than a violin because they have different overtones.

Sounds become harmful above 85 dB. According to the CDC, you can be exposed to 85 dB for up to 8 hours before it becomes dangerous, but at 88 dB this drops to 4 hours, and by the time you reach 112 dB, 1 minute of exposure puts you at risk. You don’t even have to hear such sounds for damage to occur; recent research at Ludwig Maximilian University shows that even inaudible low-frequency sounds can affect you.

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[column size=”1/2″ class=”right”]Sound can also affect you psychologically. A 2011 World Health Organization study found a correlation between prolonged exposure to noise pollution, high blood pressure and fatal heart attacks. The study also found that exposure to chronic noise, such as living near airports, canimpact children’s development and cause health and educational problems.
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[/columns]Using Sound Safely

To reduce noise pollution, turn off your electronic devices when you’re not using them to reduce background noise. Soundproof your surroundings by using rugs or carpets to cover hard floors, putting shelves or furniture against noisy walls, using curtains, and repairing or replacing faulty windows. Cancel out negative sounds by creating peaceful sounds around you. For example, you can install a surround sound or sound bar system and use it to play soothing music. Periodically take quiet time to meditate quietly and cultivate a sense of silence.

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